The present invention relates to wireless systems, and in particular, to the problem of synchronizing multicast data streams to mobile clients in the wireless environment.
Modern wireless systems operating under IEEE 802.11 standards are called upon to support a wide range of clients operating over a wide range of data rates, using different modulation types, and different protocols.
The users of these networks see, or desire to see a set of services, available on demand, wherever they are. They expect these services to operate reliably, and continue to operate as they move, for example, from one area to another in an office environment, or from one building or floor to another in a corporate campus.
Broadcast/multicast (BCMC) traffic in an 802.11 wireless network belongs to a single broadcast domain, such as one or more wireless access nodes connected to a controller. This BCMC traffic cannot be leaked or shared across multiple different domains. This BCMC traffic is usually managed according through the well known Internet Group Management Protocol (IGMP) as defined for example in RFC 1112 (IGMP V1), RFC 2236 (IGMP V2) and RFC 3376 (IGMP V3), each incorporated herein by reference.
When a mobile client crosses a Layer 3 (L3) boundary, for example moving from an area covered by one controller and its wireless access nodes to an area covered by a different controller and its wireless access nodes, existing protocols allow the wireless client to retain its IP address.
But the BCMC traffic to and from the client is restricted to a single broadcast domain. When the mobile client crosses a L3 boundary, these BCMC sessions are dropped until the client rejoins these BCMC sessions.
What is needed is a way to maintain multicast membership and sessions as wireless clients move across boundaries.